Query : 1998A&A...332L...5C

1998A&A...332L...5C - Astronomy and Astrophysics, volume 332, L5-8 (1998/4-1)

Helical structures in a Rosette elephant trunk.


Abstract (from CDS):

We discuss small-scale, helical, interstellar filaments on the basis of optical observations of an elephant trunk in the Rosette nebula. The trunk studied is composed of a number of sinusoidal or serpentine-like dark filaments, preferentially in the outer part of the trunk, where their wavelength is 7-9 times the trunk radius. The diameters are down to the limit of resolution of 1.0arcsec, corresponding to 1600au, and ranging up to about 6400au. At some positions filament crossings give rise to enhanced extinction. We suggest that the sinusoidal filaments are helices lined up by magnetic fields. We derive average extinctions of 0.5-1.0mag in the filaments, implying molecular densities of nH2≃104cm–3. From existing data on the Rosette HII region, we conclude that the surrounding kinetic and dynamic pressure and the background radiation field suffice to balance even the denser filaments and to exert drag forces on the trunk as a whole, consistent with evidence of stretching of the trunk. The helical magnetic structures imply the presence of electric currents along the trunk axis. These currents should form a nearly force-free geometry and are consistent with a model consisting of 4-7 helical cables on the surface of a cylinder and which produce the observed wavelength of the helices. We suggest that the Rosette elephant trunks form an interconnected system of rope-like structures which are relics from filamentary skeletons of magnetic fields in the primordial cloud.

Abstract Copyright:

Journal keyword(s): ISM: clouds - ISM: HII regions - ISM: individual objects: Rosette nebula - ISM: kinematics and dynamics - ISM: magnetic fields

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 NGC 2244 OpC 06 32 11 +04 54.8           ~ 587 1
2 NAME Rosette Nebula HII 06 32 26.76 +04 47 37.1           ~ 469 1
3 NAME Rosette Molecular Cloud MoC 06 34.7 +04 02           ~ 246 0
4 M 8 HII 18 03 37 -24 23.2           ~ 582 1

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